In the medical field alone, huge volumes of solutions are used everyday for uses such as wound irrigation, intravenous administrations, kidney dialysis, etc. Because of the problems inherent in the use of such large volumes of fluids, such as shipping, handling and storage, as well as sterile concerns, which tremendously complicate the other concerns, concentrates are often prepared which contain some or all of the non-liquid constituents of the finished solution. The concentrates are then diluted or proportioned with the appropriate liquid base, generally water, as close in time to the actual use of the solution as is practical. How close in time to actual use a finished solution may be proportioned is affected by a number of factors such as shelf-life of both the concentrate and the finished solution, various sterilization concerns, shipping and storing concerns, etc.
In the treatment of patients suffering acute or chronic renal insufficiency, dialysis therapy is employed. The two general categories of dialysis therapy are hemodialysis and peritoneal dialysis. In hemodialysis, the patient's blood is cleansed by passage through an artificial kidney in an extracorporeal membrane system. In peritoneal dialysis, dialysis fluid is infused into the patient's peritoneal cavity. This cavity is lined by the peritoneal membrane which is highly vascularized. The metabolites are removed from the patient's blood by diffusion across the peritoneal membrane into the dialysis solution. Excess fluid, i.e. water is also removed by osmosis induced by a hypertonic dialysis solution.
Peritoneal dialysis generally requires large volumes of dialyzing solution. Generally, at each application, or exchange, a given patient will infuse 2 to 3 liters of dialyzing solution into the peritoneal cavity. The solution is allowed to dwell for approximately 3-4 hours, at which time it is drained out and exchanged for fresh solution. Generally, four such exchanges are performed daily. Therefore, approximately 8 to 10 liters of dialyzing solution is required per day, 7 days a week, 365 days a year for each patient.
Dialysis solutions have traditionally been provided in sealed, sterilized form, ready for use. However, several substantial problems become immediately apparent. Shipping and storage of the sheer volume of fluids required is both tremendously inconvenient and expensive. Further, the repeated connection and disconnection of so many solution containers creates a very substantial risk of biological contamination at the point of connection. Additionally, tremendous amounts of waste material, in the form of empty containers and packaging, and their proper disposal are increasingly becoming matters of universal concern.
The traditional response to these problems is to use small volumes of concentrated dialysis solutions diluted with ultra pure water at the point of use. Generally, such concentrates are separated into (1) concentrated solutions containing the various appropriate electrolytes and a buffer and (2) concentrated solutions containing dextrose or another appropriate osmotic agent. The various reasons for separating the dialysis solution into two separate concentrates are well known in the art and include a number of concerns relating to sterilization.
The compounding or proportioning of the concentrates with ultra pure water back into a finished, ready to use dialysis solution are generally performed by machine. Such machines require that the user attach the source of each concentrate to a particular inlet port on the proportioning apparatus, which may be integrated into the dialysis machine itself. Generally, if the concentrates are connected to the wrong ports, or improperly connected, or one or the other not connected at all, the machine will either produce incorrectly proportioned dialysis solution or will alarm.
One such prior art apparatus is disclosed in European publication number 311,848; filed Sep. 29, 1988 in the name of Fresenius Ag. The publication disclosed a hemodialysis machine incorporating a mixing arrangement which produces dialyzing fluid by mixing a concentrate with prepared water. The mixing arrangement employs a protective system independent of the mixing system which is based upon monitoring of the conductivity of the dialyzing fluid. The disclosed system employs conductivity measuring cells placed in the concentrate inlet lines to measure the conductivity of the concentrate coming into the machine and compare it with desired values of the conductivity of concentrates to be connected. In this way, the machine will "identify" if the appropriate concentrate is connected to the appropriate inlet port. If the wrong concentrate is attached to the machine or if two concentrate containers with different concentrates are incorrectly interchanged and each connected to the inlet port designated for the other, the mistake will be sensed and the machine will alarm. Coincidentally, the sensors disclosed in the publication also act as filling level sensors.
The primary problem with such a system is that it still requires that each concentrate be connected only to a particular inlet port of the dialysis machine. Therefore, the requirement for more complicated design, and hence more complicated manufacturing, remains because the appropriate inlet port for each concentrate must be somehow identified, color coded, or even uniquely designed to nave a different shape or configuration from the other inlet port. While this prior art system may provide some increased measure of safety in avoiding improperly prepared dialysis solution, it does nothing to facilitate and simplify the proper connection of concentrates in the first place.
Moreover, automated peritoneal dialysis machines are increasingly being used by the dialysis patients themselves in their own homes to effect multiple exchanges of dialysis solutions into and out of their own peritoneal cavities, generally overnight. The individual patient/operator does not have the training and sophistication with the apparatus which is possessed by the nurse or technician. It is not uncommon for them to become confused when faced with complex machinery, particularly that one upon which their very life depends.
Further, while warnings in the event of improper attachment are vital, dialysis patients are often generally quite physically debilitated. These patients often suffer from inter alia, decreased strength and fine motor control in their hands making proper connection of the concentrate solutions, let alone repeated disconnection and reconnection of improper connections, much more difficult than for the trained professional. Their vision is often impaired, further contributing to the likelihood of improper connections.
What is needed is an improved apparatus that will accept the connection of each concentrate at any concentrate inlet port and still properly proportion the finished dialysis solution.